Reference Red Cell Serology / Obstetric Serology Tests and availability
Published on 08 October 2020
All samples referred to SNBTS for testing should be aligned to the appropriate testing pathway detailed below;
Pathway 1 ABO investigation and anomalies
Samples can be referred for investigation if anomalous results are obtained with routine grouping reagents. An extended serological investigation will be performed to investigate ABO grouping anomalies.
The genetics of ABO is complex, rendering ABO molecular typing by available methods unreliable. Where ABO anomalies cannot be resolved by serological technique, current guidance recommends that group O red cells are selected if transfusion is required. On occasion, where rare variants are suspected, individual cases may be referred onward to the International Blood Group Reference Laboratory in Filton and may require further samples including saliva.
Pathway 2 RhD type confirmation
Samples sent for confirmation of D type due to a ≤2+ reaction with one or more anti-D reagents may undergo allele specific PCR for the detections of weak D types and variant D types unless they meet exclusion criteria. This testing will be performed at the Glasgow RCI laboratory and should only be requested if the patient is under 18 years of age, of child bearing potential or is likely to require chronic transfusion support, otherwise, as per BSH guidelines, the group should be reported as Rh D positive. Samples should be sent to your regional transfusion centre for onward transport to Glasgow SNBTS if required.
Pathway 3 Antibody identification
The RCI laboratory will investigate samples with antibodies to high frequency antigens, complex mixtures of antibodies, warm and cold red cell autoantibodies. Straightforward individual antibodies and mixtures detectable with standard identification panels are not considered as reference samples and should be concluded at the local blood bank.
Samples should be sent to your regional transfusion centre for investigation in the first instance and may be referred on to Glasgow SNBTS if Red Cell Genotyping is required.
Pathway 4 Antibody quantification
RCI offers an antenatal reference service for women whose plasma contains irregular antibodies. The specificity of the antibody is determined or confirmed and the concentration is measured. If this is of clinical significance to the foetus, the antibody will be quantified (for anti-D, and c, this is performed at the Glasgow SNBTS site only) or titrated (anti-K and other clinically significant antibodies) and follow up tests performed as recommended by the BSH and RCOG guidelines. With the exception of anti-D or anti-c antibodies should be titrated at the local blood bank. Samples should be sent to the SNBTS RCI laboratory if complex mixtures result in the lack of availability of appropriate cells to allow titrations to be performed or if quantification is required.
Pathway 5 Haemolytic transfusion reaction
Pre- and post-transfusion samples should be sent for ABO typing, RhD grouping, DAT, antibody screen/identification and eluate where a possible haemolytic transfusion reaction has been confirmed and investigation has been requested by clinical haematology staff.
Pathway 6 Antenatal/renal titration
RCI laboratories can perform antenatal titrations for anti-K and other clinically significant antibodies. In accordance with BSH and RCOG guidelines, levels for anti-K should be titred every 4 weeks until 28 weeks’ gestation, then every 2 weeks until term (unless an IUT programme is instituted beforehand). Please refer to the Scottish Guidance on Management of Red Cell antibodies in Pregnancy document (2019) for further information. With the exception of anti-D or anti-c antibodies should be titrated at the local blood bank. Samples should be sent to the SNBTS RCI laboratory if complex mixtures result in the lack of availability of appropriate cells to allow titrations to be performed or if quantification is required.
ABO titrations can be performed on request for renal transplant donors/recipients to ensure that plasmapheresis is reducing the levels of anti-A and anti-B present. This thereby reduces the risk of graft rejection. ABO titrations can be performed for allogeneic haematopoietic stem cell donors/recipients. Samples should be referred to your regional transfusion centre in the first instance, they will then be referred on to Edinburgh/Glasgow SNBTS as required.
Pathway 7 DARA DTT/monoclonal therapies
Daratumumab (DARA) is a therapy for the treatment of multiple myeloma. However, DARA consistently interferes with routine blood bank testing by directly binding to CD38 expressed on reagent red cells. Treating RBCs with Dithiothreitol (DTT) helps reduce DARA interference enabling the IAT test to be performed.
DTT removes CD38 from reagent red cells so it can be used to pre-treat screening, panel and donor cells. Any reactivity of the plasma to post-treated cells should then be due to alloantibody.
To support monoclonal therapies SNBTS recommends pre-treatment testing be performed to confirm the ABO/RhD and extended phenotype, this supports the provision of blood if required. If the SNBTS laboratory is unable to obtain an extended phenotype by serological methods, genotyping can be performed. Following the start of monoclonal therapies local blood banks are recommended to perform ABO/RhD and antibody screening by manual techniques due to the potential for carry over on automated platforms. If interference is observed samples can be sent to your regional SNBTS RCI laboratory for further testing. This service request will result in a cross charge to your hospital boards in line with the current Service Level Agreement (SLA) that is in place with SNBTS.
SNBTS must be informed prior to sending samples for Crossmatch or urgent investigation. The urgency of the case must be discussed to ensure the request is prioritised appropriate to Clinical requirements.
It is important to provide details of special requirements for blood components, this will ensure that suitable components are available and prevent unnecessary delay in procurement of blood.